<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        .div1 {
            width: 200px;
            height: 200px;
            background-color: green;
            /* margin-bottom: 10px; */
            /* 上右下左 */
            margin: 10px 20px 30px;
            /* 边框 */
            border-top: 20px solid red;
            border-right: 20px solid black;
            border-bottom: 20px solid red;
            border-left: 20px solid black;
        }
        .div2 {
            width: 500px;
            height: 200px;
            background-color: pink;
        }
        .div3 {
            width: 0px;
            height: 0px;
            /* background-color: pink; */
            margin: 50px;
            padding: 10px;
            border-top: 60px solid transparent;
            border-right: 60px solid transparent;
            border-bottom: 60px solid red;
            border-left: 60px solid transparent;
        }
        .div4 {
            width: 100px;
            height: 100px;
            background-color: #f0f000;
            /* 边框圆角 */
            border-radius: 50%;
        }
    </style>
</head>
<body>
    <div class="div1"></div>
    <div class="div2"></div>
    <div class="div3"></div>
    <div class="div4"></div>
</body>
</html>